1. Field of the Invention
The present invention relates to a system and method for processing different signals on separate channels of identical, substantially identical, and close frequencies.
2. Description of the Prior Art
In direct conversion receiver designs, many receivers use multiple analog-to-digital converters to convert input frequencies while others use one analog-to-digital converter. In receivers with only one analog-to-digital converter, when two or more close or identical frequencies are processed, they may destructively combine, interfere with each other, or be indistinguishable from each other. In other words, the frequencies may combine and interfere with each other and thus not be able to be fully recovered later, and more importantly, may negatively affect the quality of the audio output to the user. This interference is especially problematic with identical frequencies, such as 95.5 and 95.5 or substantially identical frequencies, such as 95.5 and 95.7, and at times, close frequencies such as 95.5 MHz and 97.5 MHz. To avoid interference, some systems use two separate tuners and process each frequency separately, which may substantially increase the product cost.
Most existing receivers include at least one antenna capable of receiving a plurality of input signals at various frequencies. A first front end circuit and a second front end circuit is typically connected to the antenna. The first front end circuit filters out a first frequency received by the antenna, such that the first front end circuit filters all received frequencies and only outputs essentially the first frequency. The second front end circuit filters out a second frequency received by the antenna, such that the second front end circuit filters all received frequencies and only outputs essentially the second frequency. The first front end circuit provides the filtered out first frequency for processing along a first path, and the second front end circuit provides the filtered out second frequency for processing along a second path. More specifically, the front end circuits when providing a filtered out frequency generally provide a signal centered approximately in the desired filtered out frequency. The receivers also include an analog-to-digital converter connected to each of the front end circuits. If more than one front end circuit is included, typically more than one analog-to-digital converter is also included, which substantially increases the receiver cost and dramatically adds to the physical size required.